Although chemotherapeutic regimens have been useful in treating cancer, their success is limited by the often severe systemic toxicity frequently associated with their use. Similarly, cancer immunotherapeutics have shown promise for the treatment of a number of tumors and hyperproliferative diseases, but their utility is limited in situations where the tumor is relatively large or rapidly growing.
The present inventors have developed a number of DNA vaccine systems for HPV-associated cervical neoplasia as well as HPV-associated head and neck cancers. Cervical cancer can serve as a model of how a viral infection can progress through a multistep process from initial infection to premalignant dysplasia, called cervical intraepithelial neoplasia (CIN), to invasive cancer. Human papilloma virus (HPV), particularly HPV-16, is associated with a majority of cervical cancers and a subset of head and neck cancers. HPV-16 E7, one of its oncoproteins, is essential for the induction and maintenance of cellular transformation. Thus, HPV-16 E7 is an ideal target for developing vaccine and immunotherapeutic strategies for the control of HPV infections and HPV-associated lesions. However, the antigen-specific immune responses and antitumor effects generated by DNA vaccines encoding wild type E7 is weak and not enough to be effective in controlling tumor growth. To overcome the weak antigenicity of E7, the present inventors have previously created a DNA vaccine encoding HPV-16 E7 linked to the sorting signal of the lysosome-associated membrane protein 1 (LAMP-1). The encoded chimeric protein (Sig/E7/LAMP-1) also includes the signal peptide derived from LAMP-1 protein. Vaccination with Sig/E7/LAMP-1 DNA led to a significantly enhanced E7-specific CD4+ and CD8+ T cell-mediated immune responses, resulting in potent antitumor effects against E7-expressing tumors in vaccinated mice.
In addition to the Sig/E7/LAMP-1 construct described above, the present inventors and their colleagues have also previously developed several additional intracellular targeting and intercellular spreading strategies to enhance DNA vaccine potency using various immunogenicity-potentiating polypeptides (IPPs), described in further detail below. See for example, publications of the present inventors and their colleagues: Hung, C F et al., J Virol 76:2676-82, 2002; Cheng, W F et al., J Clin Invest 108:669-78, 2001; Hung, C F et al., J Immunol 166:5733-40, 2001; Chen, C H et al., Gene Ther 6:1972-81, 1999; Ji, H et al., Hum Gene Ther 10:2727-40, 1999; Chen, C H et al., Cancer Res 60:1035-42, 2000; U.S. Pat. No. 6,734,173, WO 01/29233; WO03/085085; WO 02/012281; WO 02/061113.
Among these strategies was the linkage of antigen to the intracellular targeting moiety calreticulin (CRT). The present inventors and their colleagues were the first to provide naked DNA and self-replicating RNA vaccines that incorporated CRT (or other IPPs). The present inventors and their colleagues also demonstrated that linking antigen to Mycobacterium tuberculosis heat shock protein 70 (HSP70) or its C-terminal domain, domain II of Pseudomonas aeruginosa exotoxin A (ETA(dII)) enhanced DNA vaccine potency compared to compositions comprising only DNA encoding the antigen of interest. As discussed above, to enhance MHC class II antigen processing, the present inventors' colleagues (Lin, K Y et al., Cancer Res 56: 21-6, 1996) linked the sorting signals of the lysosome-associated membrane protein (LAMP-1) to the cytoplasmic/nuclear human papilloma virus (HPV-16) E7 antigen, creating a chimera (Sig/E7/LAMP-1). These findings point to the importance of adding an additional “element” to an antigenic composition at the DNA level to enhance in vivo potency of a recombinant DNA vaccine.
Intradermal administration of DNA vaccines via gene gun in vivo has proven to be an effective means to deliver such vaccines into professional antigen-presenting cells (APCs), primarily dendritic cells (DCs), which function in the uptake, processing, and presentation of antigen to T cells. The interaction between APCs and T cells is crucial for developing a potent specific immune response.
Even if current cancer therapies are effective, there remains a need for anticancer therapies that are yet more effective.